Surface water quality in the Sinos River basin, in Southern Brazil: tracking microbiological contamination and correlation with physicochemical parameters

Around the world, enteric viruses are often found in surface waters. This study set out to evaluate the occurrence of adenoviruses (AdVs) in water samples, and its relation to different physical, chemical, and bacteriological parameters [total coliform (TC) and fecal coliform (FC), represented by Escherichia coli]. Monthly samples of 500 ml of raw water were collected from May 2011 to June 2013 in eight abstraction points water treatment stations along three stretches of the Sinos River Basin (SRB), in Southern Brazil and, subsequently, were analyzed using real-time polymerase chain reaction (qPCR). AdVs from different species, from human (HAdV), and from other animals (CAV1–2, BAdV, PAdV, and AvAdV) were detected along the three stretches of the basin, indicating fecal contamination from different sources and proving the inefficiency of the wastewater treatment in the waters of the SRB and intensifying the strong influence of human activities that can contribute to the presence of inhibitory substances such as organic acids in surface of these waters. Statistical analyses revealed no significant correlations between the concentrations of TC and FC and the concentrations of AdVs. We observed a small, nonconstant, and unstable correlation between viruses and physicochemical parameters. These correlations were not sufficiently consistent to establish a reliable association; therefore, this study corroborates that only the viral assay itself is reliable for the diagnosis of fecal contamination by viruses in environmental samples.